# 4.2.6.12. HDR¶

This command is used to construct an HDR bearing element object in three-dimension. The 3D continuum geometry of an high damping rubber bearing is modeled as a 2-node, 12 DOF discrete element. This is the third element in the series of elements developed for analysis of base-isolated structures under extreme loading (others being ElastomericX and LeadRubberX). The major difference between HDR element with ElastomericX is the hysteresis model in shear. The HDR element uses a model proposed by Grant et al. (2004) to capture the shear behavior of a high damping rubber bearing. The time-dependent values of mechanical properties (e.g., vertical stiffness, buckling load capacity) can also be recorded using the “parameters” recorder.

element('HDR', eleTag, *eleNodes, Gr, Kbulk, D1, D2, ts, tr, n, a1, a2, a3, b1, b2, b3, c1, c2, c3, c4, <<x1, x2, x3>, y1, y2, y3>, <kc>, <PhiM>, <ac>, <sDratio>, <m>, <tc>)

For 3D problem

 eleTag (int) unique element object tag eleNodes (list (int)) a list of two element nodes Gr (float) shear modulus of elastomeric bearing Kbulk (float) bulk modulus of rubber D1 (float) internal diameter D2 (float) outer diameter (excluding cover thickness) ts (float) single steel shim layer thickness tr (float) single rubber layer thickness n (int) number of rubber layers a1 a2 a3 b1 b2 b3 c1 c2 c3 c4 (float) parameters of the Grant model x1 x2 x3 (float) vector components in global coordinates defining local x-axis (optional) y1 y2 y3 (float) vector components in global coordinates defining local y-axis (optional) kc (float) cavitation parameter (optional, default = 10.0) PhiM (float) damage parameter (optional, default = 0.5) ac (float) strength reduction parameter (optional, default = 1.0) sDratio (float) shear distance from iNode as a fraction of the element length (optional, default = 0.5) m (float) element mass (optional, default = 0.0) tc (float) cover thickness (optional, default = 0.0)